Method for producing a steel tube including cleaning of the outer tube wall

Abstract

A method for producing a steel tube include the manufacturing of a steel tube having an inner tube wall, an outer tube wall (3), and a free tube cross-section enclosed by the inner tube wall. After the manufacturing, the steel tube includes at least one contaminant on the outer tube wall and entails, after the manufacturing of the steel tube, cleaning of the outer tube wall by applying liquid or solid CO.sub.2 onto the outer tube wall in order to remove a contaminant from the outer tube wall.

Claims

1. A method for producing a steel tube comprising: manufacturing the steel tube by forming a hollow shell into a form of a finished dimensioned steel tube by cold pilgering, the steel tube having an inner tube wall, an outer tube wall, and a free tube cross-section enclosed by the inner tube wall, wherein after the manufacturing, the steel tube on the outer tube wall includes at least one contaminant, the at least one contaminant being a lubricant transferred from a roll to the outer tube wall; and cleaning the outer tube wall of the steel tube by applying liquid or solid CO.sub.2 onto the outer tube wall in order to remove the lubricant from the outer tube wall, wherein, during the application of the liquid or solid CO.sub.2 onto the outer tube wall, the temperature of the steel tube is measured and the cleaning is interrupted if the temperature of the steel tube falls below a predetermined temperature threshold.

2. The method according to claim 1, wherein the cleaning of the outer tube wall is performed by CO.sub.2 snow blasting or by dry ice blasting.

3. The method according to claim 1, wherein the liquid or solid CO.sub.2 is applied onto the outer tube wall by pressurized air.

4. The method according claim 1, wherein the liquid or solid CO.sub.2 is applied in the form of a jet onto the outer tube wall, wherein a jet direction of the CO.sub.2 is substantially perpendicular to the outer tube wall.

5. The method according to claim 4, wherein a temperature of the jet is measured in the jet direction of the liquid or solid CO.sub.2 after the liquid or solid CO.sub.2 has interacted with the outer tube wall of the steel tube.

6. The method according to claim 5, wherein a velocity of the liquid or solid CO.sub.2 as it exits a feed line is regulated as a function of the temperature of the jet in the jet direction of the liquid or solid CO.sub.2 after the liquid or solid CO.sub.2 has interacted with the outer tube wall of the steel tube.

7. The method according to claim 1, wherein the steel tube is rotated during the cleaning under a jet of the liquid or solid CO.sub.2 .

8. The method according to claim 1, wherein, during the cleaning, a jet of liquid or solid CO.sub.2 is applied in a longitudinal direction over the outer wall of the steel tube.

9. A method for producing a steel tube comprising: manufacturing the steel tube by forming a hollow shell into a form of a finished dimensioned steel tube by cold drawing the hollow shell into the form of the finished steel tube, the steel tube having an inner tube wall, an outer tube wall, and a free tube cross-section enclosed by the inner tube wall, wherein after the manufacturing, the steel tube on the outer tube wall includes at least one contaminant, the at least one contaminant being a drawing oil transferred from a die to the outer tube wall; cleaning the outer tube wall by applying liquid or solid CO.sub.2 onto the outer tube wall in order to remove the drawing oil from the outer tube wall; measuring a temperature of the steel tube during cleaning; and interrupting the cleaning when the measured temperature of the steel tube is below a predetermined temperature threshold.

10. The method according claim 9, wherein the liquid or solid CO.sub.2 is applied in the form of a jet onto the outer tube wall, wherein a jet direction of the CO.sub.2 is substantially perpendicular to the outer tube wall.

11. The method according to claim 10, wherein a temperature of the jet is measured in the jet direction of the liquid or solid CO.sub.2 after the liquid or solid CO.sub.2 has interacted with the outer tube wall of the steel tube.

12. The method according to claim 11, wherein a velocity of the liquid or solid CO.sub.2 as it exits a feed line is regulated as a function of the temperature of the jet in the jet direction of the liquid or solid CO.sub.2 after the liquid or solid CO.sub.2 has interacted with the outer tube wall of the steel tube.

13. A method for producing a steel tube comprising: manufacturing the steel tube by forming a hollow shell into a form of a finished dimensioned steel tube by cold pilgering, the steel tube having an inner tube wall, an outer tube wall, and a free tube cross-section enclosed by the inner tube wall, wherein after the manufacturing, the steel tube on the outer tube wall includes at least one contaminant, the at least one contaminant being a lubricant transferred from a roll to the outer tube wall; and cleaning the outer tube wall of the steel tube by applying liquid or solid CO.sub.2 onto the outer tube wall in order to remove the lubricant from the outer tube wall; wherein the liquid or solid CO.sub.2 is applied in the form of a jet onto the outer tube wall, wherein a jet direction of the CO.sub.2 is substantially perpendicular to the outer tube wall., wherein a temperature of the jet is measured in the jet direction of the liquid or solid CO.sub.2 after the liquid or solid CO.sub.2 has interacted with the outer tube wall of the steel tube, and wherein a velocity of the liquid or solid CO.sub.2 as it exits a feed line is regulated as a function of the temperature of the jet in the jet direction of the liquid or solid CO.sub.2 after the liquid or solid CO.sub.2 has interacted with the outer tube wall of the steel tube.

Description

(1) Additional advantages, features and application possibilities of the present invention become apparent on the basis of the following description of an embodiment and the associated figures.

(2) FIG. 1 shows the cold pilger rolling mill from the prior art in a schematically side view.

(3) FIG. 2 shows a schematically cross-sectional view of an embodiment for carrying out the cleaning steps according to the invention.

(4) In FIG. 1, the structure of a cold pilger rolling mill is represented schematically in a side view. Here, the description of cold pilgering is used as an example of the manufacturing of the steel tube and as an example of how a contaminant can occur on the outer tube wall of the steel tube, which then has to be removed subsequently from the outer tube wall.

(5) The rolling mill consists of a roll stand 101 with rolls 102, 103, a calibrated rolling mandrel 104 as well as a feeding clamping carriage 105. In the represented embodiment, the cold pilger rolling mill comprises a linear motor 106 as direct drive for the feeding clamping carriage 105. The linear motor 106 is constructed from a rotor 116 and a stator 117.

(6) During the cold pilgering in the rolling mill shown in FIG. 1, the hollow shell 111 is fed step-wise in the direction of the rolling mandrel 104 and over and past the latter, while the rolls 102, 103 as they rotate are moved horizontally back and forth over the mandrel 104 and thus over the hollow shell 111. In the process, the horizontal movement of the rolls 102, 103 is predetermined by a roll stand 101 on which the rolls 102, 103 are rotatably mounted. The roll stand 101 is moved back and forth by means of a crank drive 121 in a direction parallel to the rolling mandrel 104, while the rolls 102, 103 themselves are set in rotation by a rack which is stationary relative to the roll stand 101, and with which toothed wheels that are firmly connected to the roll axles engage.

(7) The feeding of the hollow shell 111 over the mandrel 104 occurs by means of the feeding clamping carriage 105, which allows a translational movement in a direction parallel to the axis of the rolling mandrel. The conically calibrated rolls 102, 103 arranged one above the other in the roll stand 101 rotate against the feeding direction of the feeding clamping carriage 105. The so-called pilger mouth formed by the rolls grips the hollow shell 111 and the rolls 102, 103 push off a small wave of material from outside, which is stretched by a smoothing pass of the rolls 102, 103 and by the rolling mandrel 104 to the predetermined wall thickness, until an idle pass of the rolls 102, 103 releases the finished tube. During the rolling, the roll stand 101 with the rolls 102, 103 attached to it moves against the feeding direction of the hollow shell 111. By means of the feeding clamping carriage 105, the hollow shell 111 is fed by an additional step onto the rolling mandrel 104, after the idle pass of the rolls 102, 103 has been reached, while the rolls 102, 103 with the roll stand 101 return to their horizontal starting position. At the same time, the hollow shell 111 undergoes a rotation about its axis, in order to reach a uniform shape of the finished tube. As a result of multiple rollings of each tube section, a uniform wall thickness and roundness of the tube as well as uniform inner and outer diameters are achieved.

(8) In order to reduce the friction between the rolls 102, 103 and the hollow shell 111, a lubricant, for example, a graphite-containing lubricant, is applied onto the rolls 102, 103. This lubricant forms residues on the outer tube wall of the finished reduced tube. The aim is to remove this residue from the outer tube wall over the entire length of the tube by means of the process steps according to the invention described below.

(9) In the embodiment of the invention described here as an example, the cold pilger rolling mill is used in order to manufacture the steel tube, i.e., in order to form the hollow shell to the form of the finished tube. Alternatively, this forming step of the invention could, however, also occur in particular by cold drawing of the hollow shell.

(10) FIG. 2 shows a dry ice blasting of the outer tube wall 3 of a finished reduced tube 1 obtained by cold pilgering. In this dry ice blasting, lubricant is cleaned from the tube 1 which has been contaminated on its outer tube wall 3 during the cold pilgering.

(11) For this purpose, a cleaning lance 4 is directed onto the tube 1. Through the cleaning lance 4, dry snow 6 is fed by means of pressurized air 7 to the tube 1, and accelerated or blasted through an through outlet nozzle 5 onto the outer tube wall 3, so that the outer wall 3 is cleaned by means of the dry snow.

(12) As indicated by the arrows, the tube 1 is rotated about its axis during cleaning and moved linearly past the outlet nozzle 5 of the cleaning lance. However, it is unimportant here whether the tube moves or the cleaning lance 4 moves, as long as the jet of dry snow interacts during the cleaning process with the outer wall 3 over the entire length of the tube. During the cleaning process, the tube 1 is additionally rotated about its axis, so that the tube is cleaned over its entire periphery.

(13) In the represented embodiment, the temperature of the jet made of dry snow and pressurized air is measured by means of a temperature sensor 8 in the jet direction behind the tube 1, i.e., after the interaction of the dry snow 6 with the outer tube wall 3.

(14) As a result, the temperature of the “waste gas jet” behind the tube 1 is used as an indicator of whether the outer tube wall 3 has been cleaned effectively or not. If the temperature of the waste gas jet is outside of a certain temperature window, which is defined by a first upper temperature threshold and a second lower temperature threshold, then it must be assumed that the cleaning was not effective, and the cleaning process is repeated.

(15) For the purpose of the original disclosure, reference is made to the fact that all the features, as they are disclosed to a person skilled in the art from the present description, the drawings and the claims, even if they have been described in concrete terms only in connection with certain additional features, can be combined both individually and also in any desired combinations with other features or groups of features disclosed here, to the extent that this is not explicitly excluded, or to the extent that technical circumstances make such combinations impossible or unreasonable. A comprehensive, explicit description of all the conceivable combinations of features is omitted here only for the sake of the brevity and readability of the description.

(16) While the invention has been represented and described in detail in the drawings and in the above description, this representation and this description occur only by way of example and are not intended to limit the scope of protection as defined by the claims. The invention is not limited to the embodiments that have been disclosed.

(17) Variant forms of the disclosed embodiments are evident to the person skilled in the art from the drawings, the description and the appended claims. In the claims, the word “comprise” does not exclude other elements or steps, and the indefinite article “an” or “a” does not exclude a plural. The mere fact that certain features are claimed in different claims does not rule out their combination. Reference numerals in the claims are not intended to limit the scope of protection.

LIST OF REFERENCE NUMERALS

(18) 1 Tube 2 Inner tube wall 3 Outer tube wall 4 Cleaning lance 5 Outlet nozzle 6 Dry snow 7 Pressurized air 8 Temperature sensor 101 Roll stand 102, 103 Roll 104 Rolling mandrel 105 Feeding clamping carriage 106 Linear motor 111 Hollow shell 112 Chuck 116 Rotor 117 Stator